1. Field of the Invention
The present invention relates to an inverter device driving a motor and a control method thereof.
2. Description of the Background Art
An inverter device capable of outputting a voltage to a motor according to a voltage command is required in general, and in order not to generate distortion in the output voltage, an inverter device configured not to generate a deviation voltage resulting from dead time is proposed (refer to Japanese Patent Laying-Open No. 2-307369, for example).
According to the technology of Japanese Patent Laying-Open No. 2-307369, in order to prevent an arm short circuit in a transistor that is a switching element, an output signal compensating for dead time is input to a gate drive circuit of the transistor later than a PWM gate signal. The output voltage of a transistor inverter is detected, and switching delay time is measured each time. Even if the switch-on time of the transistor, the switch-off time of the transistor, or the dead time is varied, a control amount is allowed to follow this to be varied. Thus, the PWM gate signal and the output voltage signal are constantly delayed for a given period of time.
Therefore, the output voltage delayed for a given period of time in comparison with the PWM signal is obtained, and its pulse width becomes equal to the pulse width of the output voltage signal so that an output voltage error is reduced. Furthermore, a voltage is directly detected to measure a switching delay, and hence even if the amount of dead time is varied by temperature change or the like, the amount of compensation is allowed to follow this to be amended.
However, the conventional inverter device requires a voltage detection circuit to obtain the output voltage signal. Furthermore, the deviation voltage is suppressed in 2×(td−tS) period (td: dead time, tS: storage time) for each half cycle of a fundamental frequency, but there is no suppression effect with respect to compensation for a voltage caused by the semiconducting properties of the transistor or a diode constituting the switching element, the floating capacitance of the drive circuit, or the like.